Habitat

Physical Description

A darkly colored shrew with a white underside. Coloration on dorsal and ventral sides are sharply demarcated. A fringe of bristles runs along the ventral surface of the tail and on the paws which are thought to serve as a swimming aid. Teeth have red tips. Females have five pairs of mammae.

Reproduction

The breeding season in England occurs fom April to September, with multiple litters per season. Litter size can be between 3 and 12, more commonly 5 or 6. Gestation lasts approximately 20 days, and lactation twice that. Sexual maturity is reached between 6 and 8 months.

Lifespan/Longevity

Behavior

These shrew are solitary. If kept in captivity, individuals are both territorial and aggressive toward one another. They are generally active both at night and during the day, and they do not hibernate through the winter. One laboratory study found that shrews of this species mutually avoid one another much of the time, but when this does not work active antagonism can occur. They also seem to have no typical social hierarchy.

Communication and Perception

Food Habits

These shrews forage almost exclusively underwater, efficiently preying on aquatic invertebrates such as snails, mollusks, freshwater insects, and also small vertebrates such as fish, amphibians and frogs. Prey are weakened by a poisonous secretion from the submaxillary gland. They generally forage by taking a dive that can last up to 20 seconds. After coming onto land, water shrews quickly run into their burrows and emerge a moment later almost dry, after coming through the tight squeeze of the tunnel where the water is absorbed by the soil. The process is then repeated a few meters away along the stream bank. Water shrews are also known to eat some terrestrial insects as well, such as dipteran larvae.

Economic Importance for Humans: Positive

These shrews eat the larvae of insects which some humans find bothersome.

Economic Importance for Humans: Negative

No negative impacts known.

Conservation Status

Other Comments

During dives, air remains trapped between the outer hairs of the thick coat of water shrews. This greatly increases the bouyancy of this shrew.
In a laboratory experiment, a few tenths of a mg of the neurotoxic saliva killed a vole very quickly.

Contributors

Bridget Fahey (author), University of Michigan-Ann Arbor.

Glossary

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.